The effect of transient temperatures on the growth of Salmonella typhimurium LT2. I: Cycling within the growth region.

The effect of fluctuating temperatures on microbial growth is important in the passage of foods through the food chain. Suspensions of Salmonella typhimurium were subjected to sinusoidally time-varying temperatures of periods from 40 to 480 min within their growth temperature range. The change in the numbers of viable bacteria was measured with time and the experimental growth curves and average generation times compared with predictions based on isothermal growth data. The experimental average generation times exceeded the predictions by less than 30%, although the discrepancy increased with cycle frequency. Instantaneous growth rates obtained for the 480 min cycles were in agreement with those predicted from isothermal behaviour.